Outlook is slow to open

The following are a list of things you can do to increase the overall speed of Outlook

Run Microsoft Office Diagnostics

• Type Microsoft Office Diagnostics into the Start Menu run bar (Win 7)

Disable Outlook Addins

1. On the Tools menu in outlook, click Options and then click the Other tab.
2. Click Advanced Options, and then click the Other tab
3. Clear the check box next to the add-in, then click OK.

Run Outlook in safe mode

• In the Start menu run bar type: outlook /safe

Force Outlook to recreate the extend.dat file

Extend.dat
keeps a registry cache of installed Exchange Client Extensions (ECE) add-ins and their status. Resetting this will force Outlook to retrieve the settings from the registry again and reset their status.

1. Navigate to C:\Users\<user name>\AppData\Local\Microsoft\Outlook on Vista/7 or C:\Documents and Settings\<user name>\Local Settings\Application Data\Microsoft\Outlook on XP
2. Rename extend.dat to extend.old
3. Re-launch Outlook to force it to repair itself and recreate the extend.dat file

Run Ccleaner with the outlook boxes checked

• <ccleaner download link from main page>

Look for and delete large archive files

1. Go to Control Panel > Mail
2. Select and delete the data file paths

Force Outlook to use TCP/IP only when connecting to Exchange

• Outlook, by default, attempts to connect to Exchange servers with RPC (Remote Procedure Call,) TCP/IP, IPX/SPX, and even banyan vines. Meanwhile, the user is waiting for their message to display. Limiting Outlook to TCP/IP only will frequently make a world of difference in Outlook's responsiveness. To do that, you must edit the registry.
  
  Open regedit and navigate to the following key: HKLM\SOFTWARE\Microsoft\Exchange\ExchangeProviders
  Modify the key, deleting removing everything but TCP/IP, leaving just ncacn_ip_tcp.